Japanese Patent Application No. 2000-81558 filed Mar. 23, 2000, Japanese Patent Application No. 2000-206711 filed Jul. 7, 2000, and Japanese Patent Application No. 2000-355930 filed Nov. 22, 2000 are hereby incorporated by reference in their entirety.
The present invention relates to a biological information evaluation apparatus which derives blood vessel evaluation information based on a pulse waveform.
As a method for evaluating the physiological age of blood vessels which relates to the degree of arteriosclerosis and the like, an invasive method such as measurement of cholesterol or fat in blood, and a noninvasive method utilizing biological imaging techniques such as ultrasonic tomography, positron emission tomography (PET), or magnetic resonance imaging (MRI) are known.
However, invasive methods cannot be easily carried out at any time. Methods based on biological imaging technique are noninvasive, but require large-scale apparatus. Therefore, these methods cannot also be easily carried out at any time.
A known physical fact is that the pulse wave velocity in the arteries increases as the hardening of the blood vessels progresses. As a noninvasive method utilizing this fact, there is a method of judging the degree of arteriosclerosis of the aorta by measuring the pulse wave velocity, thereby estimating the arterial elasticity. However, it is considered difficult to quantitatively measure the degree of arteriosclerosis by this method with good reproducibility due to effects of the autonomous nervous system on the peripheral arterial system.
Therefore, an apparatus using an arterial pulse waveform has been proposed as a noninvasive apparatus with good reproducibility which is capable of easily evaluating the physiological age or degree of arteriosclerosis of blood vessels.
For example, Japanese Patent Application Laid-open No. 61-119252 discloses an arteriosclerosis measuring apparatus. This apparatus stores in advance a plurality of pulse wave standard patterns corresponding to the stages of hardening of the arteries. The degree of arteriosclerosis is evaluated by determining that the pulse wave detected in the artery of the living body has the greater correlation coefficient with which standard pattern.
Japanese Patent Application Laid-open No. 3-15439 discloses a physiological age measuring apparatus in which a standard pattern close to the pulse wave obtained by a pulse wave sensor pressed against the artery is selected by comparing the pulse wave with a plurality of pulse wave standard patterns which differ according to the age of the living body. The physiological age of the living body is determined based on the selected standard pattern.
These apparatuses select the standard pattern close to the measured pulse wave by calculating the correlation coefficient for the pulse wave standard patterns and the measured pulse wave. The degree of arteriosclerosis or physiological age of the living body whose pulse wave has been measured is estimated based on the degree of arteriosclerosis or physiological age corresponding to the selected standard pattern. Therefore, these apparatuses require a large capacity memory for storing a number of standard patterns. Moreover, a large number of arithmetic operations are needed for calculating the correlation coefficient between a number of standard patterns and the measured pulse wave. Therefore, it is difficult to create an apparatus small enough to be portable.
The present inventor disclose a pulse waveform monitoring apparatus for monitoring the pulse waveform and a pharmacological action monitoring apparatus for monitoring the pharmacological action based on indexing using the difference in levels between characteristic portions of the pulse waveform in International Patent Application No. PCT/JP98/05259. However, an apparatus for evaluating the physiological age or degree of arteriosclerosis of blood vessels is not disclosed in that application.
A first aspect of the present invention provides a biological information evaluation apparatus comprising:
a waveform parameter detection section which detects a specific waveform parameter based on a pulse waveform;
a corresponding relation storage section which stores the corresponding relation between blood vessel evaluation information and the waveform parameter which is derived in advance; and
a blood vessel evaluation information deriving section which derives the blood vessel evaluation information based on the waveform parameter detected by the waveform parameter detection section and the corresponding relation.
The biological information evaluation apparatus stores in advance the corresponding relation between a specific waveform parameter in the pulse waveform and the blood vessel evaluation information in the corresponding relation storage section. The blood vessel evaluation information deriving section uniquely derives the blood vessel evaluation information by applying the detected waveform parameter to the corresponding relation. Therefore, the blood vessel evaluation information can be derived without the need for a large memory capacity or a large number of arithmetic operations. Note that the blood vessel evaluation information reflects changes in organic physical property as tissue and dynamic and functional changes accompanied by the activities of the autonomous nervous system.
Another aspect of the present invention provides a biological information evaluation apparatus comprising:
a waveform parameter detection section which detects a specific waveform parameter based on a blood pressure waveform;
a corresponding relation storage section which stores the corresponding relation between blood vessel evaluation information and the waveform parameter which is derived in advance; and
a blood vessel evaluation information deriving section which derives the blood vessel evaluation information based on the waveform parameter detected by the waveform parameter detection section and the corresponding relation.
The biological information evaluation apparatus according to the present embodiment stores in advance the corresponding relation between a specific waveform parameter in the blood pressure waveform and the blood vessel evaluation information in the corresponding relation storage section. The blood vessel evaluation information deriving section uniquely derives the blood vessel evaluation information by applying the detected waveform parameter to the corresponding relation. Therefore, the blood vessel evaluation information can be derived without the need for a large memory capacity or a large number of arithmetic operations.